Several studies have been carried out on the optimization of indirect solar drying
systems, both forced convection [8–10] and natural convection [11]. In these systems,
grain at the bottom of the bed dries rapidly while that at the top is still wet due to
condensation. Optimization of indirect natural convection systems has resulted in
long collectors with thin grain beds. Recent work on the simulation of a natural
convection mixed-mode solar dryer has included the effects of the drying chamber
transparent cover through a deep bed model that combines conduction and convection
in the grain bed [6]. Oversizing the drying chamber transparent cover will make the
system too expensive but with increased drying rate while undersizing reduces the
cost but causes a slow drying rate. Optimization of the collector and drying chamber
dimensions is, therefore, essential to make effective use of the mixed-mode solar
dryer.